Special-call telephone system.



A. E. KEITH. SPECIAL CALL TELEPHONE SYSTEM.

Patented Feb. 4, 1913.

' APPLICATION FILED MAY 2, 1911. 1,051,894.

3 EHEETS-SHEET 1.

42mm 8. M

a, 66 Ma MTYVESSES A. B. KEITH.

SPECIAL CALL TELEPHONE SYSTEM;

APPLICATION FILED MAY 2,1911.

1,051,894, Patented Feb. 4, 1913.

3 SHEETS-EHEBT 2.

N g llllllllllllHl W/TA Zlfi'SES F f/VKENTOK:

A. E. KEITH SPECIAL CALL TELEIHfiNE SYSTEM.

APPLICATION FILED M A w I UNITED STATES PATENT OFFICE.

ALEXANDER E. KEITH, OF HINSDALE, ILLINOIS, ASSIGNOR TO AUTOMATICELECTRIC COMPANY; OIICHIOAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

SPEOIALCALL TELEPHONE SYSTEM.

Specification of Letters Patent.

Patented Feb. 4, 1913.

Application tile d May 2, 1911. Serial No. 624.558.

To all whom. it may concern:

Be itknown'that I, ALEXANDER E. KEITH,

. systems in which either all or adpart of t ie callin connection .isestablishe by means contro led by the calling subscriber, and more esecially to a system of this kind in .which t e automatic switches arecontrolled by rotary or other similar calling devices atthe substations.In such a system it is necessary, of course, in order to extcndthe-callfrom any calling line, for the calling subscriber t0 first take down thereceiver, and to then operate the rotary or other suitable callingdevice, whereby either all or a part of the calling connection is thenextended from the calling line. Ordinarily, in a s stem of thischaracter, a calling subscri er cannot obtain connection with thesubstation of any other subscriber, or even with the telephone of anexchange 0 erator,'e'xeept by first operatin the 'sai rotary 'or ot iercalling-device at e callin substation. In some cases this is extremely ojectionable, as itoften occurs that-a callingisubscriber should have ares case as quic ly aspo sible, and without. eing under the neoessi y offirst operating the rotary callin device.

The ob ect of my invention is, t erefore, to provide a system of thisdgeneral character in, which, revision is ma for'en'abling a calling ascriber. to converse-with an oporator without the necessity of -firstoperatin the rotary calling device at the calling su station. n..thisway, for example, an alarm of tire can be turned in very quickly and simly' byfthe removal of the receiver at the ca ling substatiom Also, .thisexpedispecie cat can be employed. .for enabling an call .E

ing subscriberto converse with a ou le op-' erator ,orwithpan-operatorIforfsome other l purpose, by simply. takingdownthereceiver at the calling substation, and without the necessity of firstoperating thelrotary calling device. Regular calls can be made in tli'e, usua l.way v "W c J in the well-known manner.-

each callin meets and t isconnects, through the medium In Fig. 1't

operating the rotary But calls for certain special purposes, such asthose indicated, or of any .other desired character, can lie-made bysimply removing the receiverat the calling substation.

To these and other useful ends m tion contemplates a telephone witinvenwhich subscriber automatically conof switching mechanism controlledfrom the calling substation, before the call reaches the called line.

It further contemplatesa telephone which is common to a plurality offirst selectors, being connected therewith, and which is automaticallydisconnected from the calling line by the initial operation of any firstselector, whereby the said tele hone is connected with each and everycal ing line, and then automatically disconnected therefrom by theinitial operation of the selector before the call reaches the calledline.

It further contemplates a system in which means are provided forenabling an operator to listen in on every calling line as soon as thereceiver is removed at the Calling substation, and in. which means areprovided for preventinf: the operator from listening in on any cal inlines overwhich the calls have pro esse' to the point where the rotaryca ing device has been operated to control the automatic switches.

In the accompanying drawings, Figures 1 and 2 taken together show acomplete connection between a-calling substation A and a calledsubstation A in a systemin con- .neotionwith which I have chosen toillus- 'trate my invention.

Fig. 3 is a diagrammatic representation of a portion of the centralotfice ap aratus.

lie lines of the substation A terminute at the central oflice in anindividual or line switch 0. The line switch 0, together with a numberof similar switches, is controlled by-a socalled master switch D and hascommon access to a plurality of trunk lines leading to first selectorswitches A group of-firstselectors E has common access to, anumber' ofsecond selectors F, which in-turn have'access to connector switches L.The'connectors have direct access'to the subscribers lines. Theconnector- L is represented as having been brought into connection withthe e of substat1on-A'.-to which there is allotted at the centralotll'oe thezline switch C'.,

5 prises-theusual receiver 2, switch hook 3 .At -:(Fig. 1);:there. isrepresented an ope'rators-talking set a I jThe' automaticsubstation withwhich I have chosen to'illustrate my invention comtransmitter;4,;iringer, 5' and condenser. 6. Since it ,is 'an-autom'atic substation,-.itis provided with a'pair ofimpulse springs 7 and 8 and an impulsewheel 9. The impulse wheel9jcarries on'its periphery a number of impulseteeth 10 'and is secured to a shaft 11, towhich there is also secured adial; (not shown) rovided with. fin er holes.. By m'ea'ns'o the dial theimpi se whcclmay be rotated forward, after which it may be returned tonormal ppsition by a spring (not shown). During t s backward movement oftheimpulse wheel, each of the teeth 10 which passes the end of thespring 8 momentarilyseparates said spring from the a ring 7. The numberof teeth which are t as carried net the end of the spring 8 dependsupon't e digit called.

The line switch C, which is individual to the line of the substation A,and the master switch.D are of the general type disclosed in BritishPatent No. 26,801 0 1906, and in the. American Telephone Journal of NewYork, N. Y., of J une 6, 1908, buthaving a somewhat modifiedconstruction. As illustrated herein, the line switch C comprises theusual plun er 12 (Fig. 3) attached to the end of the 'p unger arm 18,which is controlled by the magnet 14. Besides the lunger arm 13, themagnet 14 also contro s the relay armatures 15 and 16, and comprisesfour windings, namely, a pull-in winding 20, a holding and cut-offwinding 17, a line winding 18 and an auxiliary winding 19. The core ofthe magnet 14 is provided with a lateral projection 21 near the centerof its length, by means of which the ma et is attached to the bracket 22upon which the armatures 15, 16 and 18 are mounted. With thisarrangement the magnetic circuitpf the windings 17 and ismadesepara'tefrom that of the windings 18 fore the armatures on one endof the magnet are not affected by the windings upon the other end. .Ofthe, two windings u on the upper: end of the ma et, the --winding 20 isthe stronger and, w en energized,-opcrates both the'pl ture -15. qThe' wnding 17 is strong enou h to" perate only, the armature 15qand 'ho dthe-plunger'arm 18 in operated 'tion. It'cannotattract the plunger armin its normal is attracted, the plunger on the 'end'thereof is forcedinto'a grou "of rings, forcing the springsm}, 25, .2 and 9-into mentwiththesalringfi 24, 26, 28 and 8, llpectivelyr Al oug only one 'grou of(ea-soil. shown, each. switc C es'g iiied wi number of suchgrqnns and19, and there-,

unger arm 18 and arms positiom When the plunger arm 18 of s rin eachgroup forming the terminal f a t runk line leading to a selector E. Eachof these trunk lines is common to a number of line switches C. Theplungers of idle line switches normall engage a socalled plunger shaft31 ig. 3), through the 'medium of which they are held oposite idle trunklines by the master switch which is common to a grou of line switches.As herein represented t e master switch D com rises, among ot erdetails, a ratchet wheeP32, motor magnet 33, relays 34 and 35 and a bankof contacts comprising a common segment 36 and an indivi ual segment afor each of the trunk 30 lines to which the switch C has access. Theratchet wheel 32 is connected with the plunger shaft 81 (Fig. 3) by thelink 87 and shaft 88 in such a 'manncr that the rotary motion of saidwheel imparts td the plunger-shaft 81 an oscillator motion about-theshaft 38, to move the idle plungers back and forth in front of the trunkterminals. Attached to the shaft 38 there is a locking plate 39,provided near its outer no edge with a number of o enings 40 which areadapted to be engaged by a pin 41 on the end of the armature 42 of relay35. The openings 40 are so spaced that the pin 41 can engage one, ofthem only when the plunger-s which are in engagement with the pin ershaft are directly opposite the-termin fis of a trunk line. Attached tothe shaft 38 there is a wiper 43 which always keeps the common seconnection with the individual segment a which corresponds to the trunkline in front of which the idle lungers are being held by the lungershait 31.

The rst selector E is of the disclosed in United States Letters'Patent815,321, granted March 13,1906, to Keith, rickso'n. and Erickson, beingsomewhat modified, however, in' order system in which the central iscontrolled from'the calling substation over the two .sides' of the linein series. This selector comprises the usual wipers 44, 45 and 46,carried upon a shaft (not shown) to operate in a 'thevertical ma et 47and a rotary motion controlled by t e rotary magnet 4.8. The usual side.switch, comprising the wipers 51 and 52, is controlled by the privatemagnet 53 in a' well-known manner. leasing the switch are providedin'the usualrelease magnet 56; 'T e springs 57 and 58 which'are includedin the circuit of the release magnet are separated by the arm 59,

as said shaft is in its lowest position. The s rings 187 and 188 areheld in contact by t 0 arm 59 as long as the switch shaft is in itslowest position, but become separated as tsoon as the shaft is raisedone or more steps.

ment 36 in electrical general type office apparatus 11L which .has avertical motion controlled by Means for rewhich is attached to theswitch shaft, as long The inechanisinof the selector E is releasedimmediately upon" the energization of the release magnet', fra ther thanb its deenergization'as shown in the said se ector patent. The armature60 of the rotary magnet 48 has no finger for pressing down the armatureof theprivate magnet 53, as shown in the selector patent, but controlsthe said private magnet electrically through-the medium of the springs.49 and 50. The. calling subscriber controls the operations of theswitch through the medium of the double wound line relay 62. The relays-63' and-64 are relays that de'cnergize slowly after their energizingcircuits have been broken. This slow action is usuallyobtained bysecuring a heavycopper rip around one end of the core of themugn'et. hewipers of the selector E are adapted to en age a bank of contactsforming the termina s of trunk lines leading to selectors F. Each trunkline is commonto a number of selectors E. v

' The selector F is like the selector E, with the omission of the ofinormal springs 137 and 138.

,The operators' talking set 0 (Fig. v1) comprises a receivcp 139.transmitter 140 and induction coil 129.' Thisoperators set is common toa number of first selectors E. Allotted-to eachselector there is a relay136 for establishing a talking connection between the operators set andthe selector.- The connection between the operators set and the selectoris also controlled by the springs 1-87 and 138 which are controlled.

t. ie arm 59 in the manner already ex laine The connector- L"(Fi v3)' isof.t e general type disclosed in U iited States-Letters Patent :815,1'2'6, granted March 18,1906,

to Keith,'Ericl-rson and Erickleon but; like-'- the selectors, is'm'odifiedsome'whatto oper-- ate in a two-wire system. Liketheselectors, the 'connector comprisesjaset oi wipers 103,

104- and 105carried upon a shaft-'.(not' shown) which is control edbythe vertical magnet 107 and ,rotary ma usual side switch is controllebythe' rivate magnet 108 in the usual manner. he release,.magnet109"-issimilar to-the release magnet 01 the, selector switch. The ringer,

relay =110is provided for the piurpose of connecting theringer'generator withthe called line afterfconnection'haa beenicompletedtherewith. The talking-batteryciir rent is fed to thecalledrsubstationthrough the winding of'the'so callediback brid' relayj;111. Thetalking circuit throng the connector includesitwocondensers vi112. and

Having given a general description of the apparatus, I- will nowdescribe its operations in detail. It will'.-first be explained how acal ing subscriber A obtains connection with another subscriber A, afterwhich itwill be described how's subscriber may communiet 106. The

cats with the operator at O; .In order to call' another subscriber thecalling subscriber must first remove his receiver and then operate hiscalling dial'for, each of the digits of the number of the line desired.In-order to communicate with the operator, all thatthe-callingfsubscriber need do is s imply remove his'receiver fromtheswitch hook.

assumed that the number of the Substation A is 2220. When-the receiveris're noved from the switch hook preparatory to making a call, the saidhook rises, permitting spring 211 to disengage spring 213 and en'- gagcspring 212, whereby the circuit of' the na bi'i ge consisting of thetransmitter .4, teceiver 2 and' iinnilse springs 7 andtBis closed'acrossthe ine conductors 66 and 67. This completes an ener izing circuit forthe line winding 18 of' te line-switch C. This circuit Extends fromthrough springs 68 and 69, line. 67, hook switch springs 211 and 212,impulsesprings 7 and 8, receiver, 2, transmitter 4,'line' 66, sprin s71and and winding 18 to batt'ery end 74, thence through the battery 13 toground G. The winding'1 8," upon enerizinig, attracts the armature 16,which orces'the spring 73 into engagement. with spring 68, therebycompleting a circuit t '16 from breaking the circuit of the winding-following manner: The .forcin 23. and 25. into engagement with springs24 and 26, respective ,'by the plungeroithe sw tch 0 extends t e lineconnection tb the selector E,'whe reby' the relay. 62 becomes energizedover. a circuit extending from ground Gthrough the lower winding ofsaid'rela springs 101 and 102, s'prings'26 and 25, t ence to andthrough-substation A and back over the other side of the line, throughthe line switch springs '23 and 24, springs 134 and 135, u per windingof relay 62. and lower wincing of relay 13 6 to In the followingdescription it will be' r 5 and condenser (E is'bi'oken, an'd a/ groundG deenergize. slowly'to prevent thearmature 20 before-the circuit of theholding winding ;17 is closed. This circuit is closed-in the of springsthe battery lead 74. The'relay 62, upon energizing, completes acircuitif rom ground use 'attractsita armature 42, withdrawing ethe'plungerauntil the'ncx't opening in the said *circuit extending, from;through sprin s-' 81' and 82,

'by'the switch 10 had been busy,

G 'through springs 78 and-79 and relay 63 to the battery lead"74. Therelay 63, upon energizing,complctes the circuit of the holding winding'17 of the line switch C, ound G I I 8 and 27, andiwindin'g 1 to battery.lead 74. -The current in winding 17 serves to. hold the plunger'arm'j13.and'.farmature. 15 in an operated 'osition'a'fter-the circuit ofwinding'20 is roken by the falling back of the armature 16.--Theenergization of the relay 63' at the selector E also extends a guardingground over the conductor 83 to the private ank-contactsof' the callingline in the banks of all connector switches WhlCll have access to thatline.

I The engagement of the line-switch bank springs 29 and 30 completes anenergizin circuit for the relay 34 of the master switc D.. This circuitextends from ground G through springs 29 and 30, contact 84, wiper 43,segment36 and relay 34 to battery lead 74. The relay 34, uponenergizing, operates to close the circuit of relay 35, which in tufln te pin 41 from the plate 39 and comp ting the circuit of the motor ma et33. This circuit extends from. groun G through magnet 33,.interruptersprings 85, contact point 80 and armature 42 to battery lead74. As long as the armature 42 engages contact point 86, the magnet 33operates in a manner similar to that of a buzzer, to rotate the ratchetwheel 32 to advance the plungers that are in lockin engagement with theplunger shaft. A ter the plungers have een advanced a short distance,the wi r 43 passesoff the contact 84, thus allowing the relays 34 and 35to deenergize. The armature 42 does not fall back immediately upon thedeenergization of relay 3:"), because the o ening in the. plate 39 whichwas engage by p in 41, has-passed out of register therewith; {After therelay 35 is deiin'ergized, the master switch still continues to advancelate 80 paseesa nder the pin 41, whereupon, itthe corresponding'trunk,line isidle, the pin 41 drops into said opening, locking the plungershaft against. further rotation and allowing" theiarmatur'e' 42 [todisengage contact oint 86'- to break the circuit of magnet 83, fthe-next trunk after the one'eeized th w p 48 would have-foundthe corresending con grounded,

energized while the next opening was pass in under the pin 41 therebycausing the id e 1plungers to be-advanced past the busy trun ,to, an-.idle one. .Duringthe time the masterfswi'tch D is operati the all-inwin I 20o! all the line sw escon rolleda I master ,are

from the battery and connected to the busy signaling machine M. Thus anysubscriber who attempts to make a call while the plunger of his lineswitch is being moved from one trunk to another will not be able tooperate the line switch, but will receive a busy signal, due to theinductive relation of the line winding 18 to the winding 19, which isconnected to the busy signaling machine.

The foregoing are the operations which take place immediately upon theremoval of the receiver at the calling substation. The callingsubscriber now operates his calling dial in the usual manner for thefirst digit 2 of the number desired. As the impulse wheel 10 returns tonormal position after being rotated with the. dial for the digit 2, theimpulse springs 7 and 8 are momentarily separated twice. The separationof the impulse sprin 7 and 8 breaks the energizing circuit of t isselectorJine relay 62, allowing it to be momentarily deinergized. Sincethe relay 63 is slow acting, it does not have time to denergize duringthe momentary interruption of its circuit by the dener m'zation of therelay 62. Consequently, the de energization of the line relay com letesan energizing circuit for the vertica magnet 47. This circuit extendsfrom ground Gr through the springs 78 and 80, springs 87 and 89,- relay64, vertical magnet 47 and side switch wiper 51 to the battery lead 74.Since the digit called is 2, the vertical magnet receives two impulsesover this circuit, operating to raise the shaft and wipers two steps toa osition opposite the second row or level of bank contacts. The relay64,

which is included in the energizi circuit of the vertical magnet, isenergize by the first impulse through it, but, being a slow actingrelay, its circuit is not opened long enough to permit it to deiinergizeuntil after the last impulse forthe digit is transmitted. In itsenergized position therela 64 closes a circuit extendin from oundthrough the springs 90 an 91 an private magnet 53 to the battery lead74. After the last impulse for the first digit is transmitted, the relay64 deenergizes and opens, the circuit of the private magnet, whichinturn deenergizes and permits the side switch to pass toseeond'pos1t1on.' In ssing from first to sec- 'end position the. sideswitch wiper 51 diaconnects the battery from the vertical magnet 47 andclosesa circuit throughtherotary magnet 48. This circuit extends from'ground G through interrupters rings 50 and 92, rotary magnet 48 and sideswitch wiper 51 to battery lead 74. The magnet 48, upon energizing,attracts its armature 6,WhlCl1 rotates the switch shaft and wipers oneopens the circuit of its own magnet at e interrupter springs 92, andcloses the circu t of the I I I I rivate magnet 53 by forc ng spring 50mto engagement with grivate magnet I 8 G from thepriva'te magnet. If.the first trunkupon the contacts otwhichthe selector wipers have justbeen rotated is idle, the

etinergizes when the ground is disconnected and allows the side switchto ass .to third. position. If, howover, the rst trunk is already inuse,the private wiper 46 finds the first contact which it engages grounded,and maintains the private magnete'nergized-over a. circuit extendingfrom said grounded bank contact through .the wiper 52and magnet 53 tobattery lead 74; The private magnet thus locks the side switch in secondposition, and the rotary magnet continues to'operate in a manner similarto that of a buzzer to advance the wi rs ate by step until the privatewiper 4 engage a non-grounded con tact of an idle trunk, whereupon theprivate magnet deenergizes and permits the third position. At

side switch to pass t the instant the side s ptch asses to thirdposition a guarding po entia is established at the selector private bankcontacts'of the trunk seized by the selector E. This arding potentialextends from groun G through the springs 81 and 82, side switch wiper 52and private wiper .46 to the selector private bank contacts. The passageof the side switch; wiper to third position also completes an energizingcircuit for the relay 98. This circuit extends from ground G" throu hthe springs 81 and 82, relay.

98.-and si e switch wi er 51-to the battery lead '74. The rela 9thereupon energizes and, by. shifting t e springs 102 and 134 out of engement' with the s rings 101 and 135 and into, contact with t e springs93 and 94, respectively, disconnects the line relay 62 from the line andextendsconnection throu h the shaft -wi era 44 and 45 to the seconselector F. T e rela 62 thereupon detinergizes and disconnects t eground from the slow acting'relay 68, which dc'einergizes anddisconnects the round Ci from the relay [98. Before thishappens however,a new holding circuit is provide for this relay by the selector F in thefollowing'manner: As soon its connection is, extended to said selector,its line relay 95 becomes ener- I gized in the same manner-in which therelay 62 of the selector E-was ener zed when the connection wasfirstexten'de thereto. The relay 95, u'pon energizing, completes acircuit throu ith'e'slow, actmg relay 96, which corrcspon stotheffr'clay68 of selector E. The relay 96, uponenergizing com letesthe circuit from ground G. throng] the springs 97 and 99, conductor 210,)rivate wi er 46, side sw1tchwiper-52,4rc ay 98 and side switch wiper 51to the battery lead 74. The energization otthe relay 96 of the selectorF also provides a holding circuit for the winding 17 of the line switchC after the relay 63 of the selector E' has deene'rgized. i

When the calling subscriber operates his calling device for the seconddigit 2, the

circuit of the line relay 950i the second selector F-is broken twicebythe substation impulse springs 7 and 8. The selector F operates inresponse toflthese impulses in exactly the same manner as explained forthe" selector, E to raise its wipers two steps and then to automaticallyrotate them onto an idle trunk line 131-132 leading to a connector L.-The relay 114' of the selector F is then energized in the -same-manneras-explained for the relay 98 of the selector E and disconnects the linerelay 95 from the line. The relays 95 and 96 thereupon deenergize,causing the ground Gf to be.dis-

connected from the trunk release conductor 210. Since the relay 96 isslow actin a new holding ground for the switches and C is provided b theconnector L before the said relay 96. as time to deenergize. Thisholding ground is rovided in the fol-' lowin manner: When t e connectionis extende to the connector, its liner'elay 145 becomes energized in.thesame manner as the line relays95 and 620i the selectors F and E. Therelay 145, upon energizing,

completes a circuit extending from ground G through the springs 151and152' and slow acting relay 154 to the battery lead-74. The relay 154,upon energizing,- completes a circuit from ground G through springs 115and 116, conductor 117, private wiper 118 of selector F (Ei 1), sideswitch-wiper 119, conductor 210 mm which one branch extends through t erelay 114 to battery, while another branch extends to and throu h therelay 98'of'-.the selector E and also t rou h the holding winding 17 ofthe line switc C to batterg'; When thecallin su scriber operates hiscalling device for t 'e third di it 2, the circuit of the connector linere ay is broken twice momentarily. Each time the relay. 145 deenergizes,a circuit is closed extending from ground Gr throughthe sprin 151 and156, 160 and 161 sthe slow acting re ay I54'remaining operate during theentire time the relay 145 is operating), the vertical magnet 107, sideswitch wiper 162 and private magnet relay 163 to the battery lead; Thevertical magnet 107 receives two impulses over this circuit and opteratsin response. thereto to raise the aha wipers 104, 105 and 103 two steps.The private ma et relay'163 is energized by the first impu se to thevertical magnet and, being a slow acting rclay, remains in its energizedposition lmtil the last impulse is transmitted. In its'cnergizcd circuitrom ground (1" through springs position, the relay 1,63 completes a a164 and 165 and private magnet 108 to the battery lead. \Vhen theprivate magnet relay 163 denergizes after the last impulse is deliveredto the vertical magnet, it allows the rivate magnet 108 to dencrgizealso, whici causes the side switch to be tripped to second position. Theside switch wiper 162, in passing from first to second position,transfers the battery connection from the vertical magnet 107 to therotary magnet 106. Now, each time the line relay 145 deenergizes inresponse to the operation of the substation calling device for the lastdigit 0, the rotary magnet 106 is ener ized over a circuit extendin fromgroun G" through springs 151 an 153, 160 and 161, magnet 106, springs166 and 167, side switch wi er 162 and rela 163 to battery. Since thelast digit is 0, t a rotary magnet receives ten impulses, thus causingthe wipers to be rotated ten ste s onto the contacts of the desiredline, 0. 2220. The private magnet relay 163 is energized in series withthe rotar magnet and remains in its operated position until after thelast impulse has been delivered. The private magnet 108 is thusenergized as soon as the rotary magnet be ins to operate, anddeenergizes shortly 9. er the wipers have been rotated onto the calledline. This operation of the private magnet causes the side switch topass from second to third position in the usual manner, therebycompleting the connection from the calling to the called substationthrough the medium of its wipers 168 and 169. The side switch wiper 170,in

its third position, provides an energizing circuit for the cut-offwinding 194 of the line switch C, and a guarding potential for theconnector private bank contacts of the called line, extending fromground G through said wiper 170, springs 171 and 172, private wiper 105,thence to the connector private bank contacts and over conductor 173 andthrough winding 194 to battery.

The winding 194, u on energizing, attracts the armature 195, w ichoperates to disconnect the line switch 0' from the called line.

and to complete a connection from the connector bank contact 196 to .theline conductor 185.

The side switch wiper 162, in passing to third position, com letes acircuit extending from ground through the interrupter 174, springs 175and 176, ringer relay 110, side switch wiper 162 and relay 168 tobattery. The relay 110 is intermittently energized over this circuit,each time operating to disconnect the calling from the called line andconnect the ringer generator M with the called line. Rin 'n current thenflows from one termina 0 said nerator through the ringer relay sprin 77and 178, si e switch wiper168, sha t wiper '108, springs 188 and 184,line 185,

ringer 186, springs 187 and 188, line 189, wipers 104 and 169 andsprings 181 and 180 back to the generator M. When the called subscriberremoves his receiver from the switch hook, or as soon thereafter as theringer relay 110 deenergizes, a circuit is completed extending fromground G through the side switch wiper 170, lower winding of theconnector back bridge relay 111, ringer relay springs 182 and- 181,thence over the heavy conductor to the hook switch spring 188 at, thesubstation,.spring 190, t ence through the transmitter and receiver backover the other side of the line to and through the ringer relay springs178 and 179 and the up r winding of the connector back bridge rdll iy111 to battery lead 74. This circuit supplies the called substation withtalking battery current and also causes connector relay 111 to energize.The relay 111, upon energizing,- byso arating the springs 175 and 176,opens t e circuit of t e ringer rela 110 so that the generator will notbe again connected with the called line-after the receiver has beenremoved from the switch hook at the substation A. The two subscribersmay now carry on an uninterrupted conversation over the talking circuitwhich is outlined by heavy lines in Figs. 1 and 2, the callingsubstation being 95 supplied with talking current through the connectorline relay 145, while the called substation receives talking currentthrough the relay 111, as described. The release 1" all of the centralstation apparatus is rought about by the hanging up of the receiver atthe calling substation when the conversation is completed. The hangingup of the receiver destroys the energizing circuit of the connector linerelay 145 by the separation of the hook switch springs 211 and 212. Therelay 145 upon deiinergizing, breaks the energizing circuit ofthe'connector release relay 154.. The relay 154 thereupon definergizesand, by permitting the spring 160 to en age spring 191, comletes acircuit for t 0 release magnet 109. his circuit extends from ground Gthrough the springs 151 and '153, 160 and 191, magnet 109 and springs192 and 193 to battery. The magnet 109, upon energizing, immediatelyrestores the mechanism of the connector ,to normal position. When theconnector shaft reaches its lowest position, it separates the springs192 and 193, thereby a lowin the magnet 109 to deenergize. The eener'zation of the' relay 145. also disconnects e ground from the trunkrelease conductor 117, which ermits the relays 114 and 98 and thewinding 17 of the switches F, E and C, respectivel', to detinergize. Thede iergization of t e winding 17 permits the, lunger of the line switchC to be restored to normal position. The deenergization of the relay 1201 whenever'a line lS- busy there is a guardthrough its lower winding,and operates ,in conjunction with the magnet 108 and the 98 ot theselectorE completes a -circuitfextending from ground G? t rough thesprings 78 and 80, 87 and 197 198 and 199, 57 and 58 and magnet, 56 tobattery. T he-magiiet 56, upon deenergizin immediately releases theselector file deenergization of the relay 114 causes .the release of these- .lector B 'in the same manner as just. de scribed for the vselectorEwhen its, relay 98 selectors reach their lowest positions, the cir-'cuits of their respective release magnets are broken in the same manneras described forthe connector, and all apparatus em iloyed in theconnection isleft in readiness or an-- other call In the foregoingdescription it was assumedthat the line of the called substation 'A' wasidle when called by the subscriber at substation A. In case this linehad been busy, the connector B would not have completed connectiontherewith and the calling subscriber would have been given-the busysignal in the following manner: It is evident from the previousdescription that ing ground potential u on its connector private bankcontacts. T as it will be seen that at the instant the wipers of theconnector L arerotated onto the contacts of a busy line, a groundconnection is extended from the guarded private bank contact of saidline through the wiper 105, springs 172 and 171, lower winding of therelay 111, ringer relay s rings 182 and 181, side switch wiper 169 (wiich is then in second position) to the sprin 200 of the relay 163. Asthe relay 163 den'ergizes after the last impulse for-the last digit hasbeen delivered, the spring 165 engages the spring 200 before it isdisengaged from the spring 164, and

l the private magnet 108 does not-deenergize, but remains locked inseries with the lower winding of the back-bridge relay 111. The relay111 also becomes operatively energized relay 163 to complete a circuitextending from'ground G throii h the springs 164 and 201, 202 and203,,rc av 204 and springs 205 and 200m battery. The relay-204, uponenergizing, disconnects the private wiper from the magnets 111-and 108and substitutes therefor the ground G". This prevents the private magnetfrom dei nergizing and completing the connection with the called line incascthe guarding potential should l)e'rcinov d' froni its private bankcontacts before ,tlieQconncctor is released. The relay 204. inits'e'n'ergizccl position. also 1 completes a circuit over which thecallin" subscriber receives the busy signal.. This circuit extends fromone teruiuial of the busy i i alln machine N tnrough springs 207 in 20s0 relay 904, contact 'point 20,

deenergized. When the switch shafts of the side switch wiper 168, thenceover the heavy .condiictors to and through substation A and back overthe other side of the line, to and through the connector line relay 145to ground G, thence through the battery B tothe battery lead 74 and totlie other-terminal of the busy signaling machine. Since the privatemagnet'is not allowed to describer, by hanging up his receiver, mayrelease all-of the switches in the same manner as when a successfulconnection has been made.

In the foregoing it has been explained howa calling subscriber mayobtain connection with any other subscriber iii the system by operatinghis calling device for t e successive digits of the number of the linewanted. It will now be explained how, in case of eiiiergcncv, asubscriber may ob'- tain connection with an operator without operatinghis calling deviccat all. It will be remembered that, when the callingsub-' scriber removes his receiver, the line switch C operates to extendthe connection to the first selector E, whereupon its line relay 62becomes energized over a circuitwhich includes the transmitter of thesubstation A and the lower winding of the relay 136. This circuit,therefore, furnishes the calling substation with talking battery currentand also causes the relaylilti to energize. The energization of thisrelay completes the secondary circuit of the operators set'O. Thiscircuit extends from one terminal of the secondary winding of theinduction coil 129 totlie up er winding of relay 136, springs 127 an128, 137 and 138 and rc-- ceiver 139 bacl to the coil 129. The .twowindings of the relay 136 also form an iiiductive connection between thesubstation talking circuit and the secondary circuit of the operatorsset, whereby the calling subscriber may converse with the operati Itwill thus be seen that every calling subscriber is put into connectionwith the operator as soon as he removes the receiver to a bell. lamp orsuitable signal in case it is A desired to provide an audible or visualsignal to attract attention if there should be no one listening on theoperators set who" a call comes in.

It will be seen therefore, that by-my invention I-prpvide an-arran outfor ens bling an operatorto-listen 1n onall lines-as soon asthe.receivers at'the submit-1L tions thereof are removed from their switch 1books, and inwhich means are providedjtor preventing the operator fromlisteningin on any calling lines over which thecalls-have progressed tothe point where the notaryfl calling device has been operated toobntrohthe automatic switches. Thuseach and, every calling line is momentarilyconnected "with the operators tele hone, regardless of the character ofthe "cal and if the calling subscriber wishes atanyitime'to conversewith the operator no operation of the rotary calling device at thecallingJsubstation Lie necessary. Each calling line is initiallyconnected with the op'erators telephone, but the initial'operation ofthe first selector disconnects the operators telephone from the callingline, whereby the call may then progress in the usual manner, andwithout the possibility of the operator listening in on the connection.The operators telephone can be located at a manual.switchboard, or atany other suitable point in the system, and every calling subscribercan, fore operating the rotary calling device, attract the attention ofthe operator by simply speaking into the transmitter at thecallingsubstation. This is useful, for example, in turning in firealarms, or in conversing with" a trouble operator, or for various otherpurposes. Every call that goes through the exchange must make a passingconnection, so to speak, with the operators' telephone. If the callingsubscriber desires to converse with the operator, then thecall stops atthat point. On the other hand, if the call is regular, and from one lineto another, then the call immediately passes on and finds the calledline. In every case, and when the calli and called lines are finallyconn nectecl the operator is cut oil and cannot overhear theconversation. Thus, for certain purposes at least, anpperator is givensupervision of the a stem without entailing any :additional 'wororeflort on the part of the subscribers. A subscriber may at any timeobtain the. attention -and services of an :operator,

at this does not necessitate any additio 1 devices at the substations.

\Vha I claim as my invention is:- 1. In a telephone system, a pluralityof 'teleph one lines, mechanism operable under substation control toextendconnection from calling lines to called lines, and disconnecttherefrom,a telephone common to all of said lines, means for connectingsaid telephone with a calling line,'andmeana controlled by the operationotsaid mechanism.

telephone lines, mechanism operable undersubstation control to extendconnection from callin lines to called lines, and disconnect there rom,an operators board common to all of said lines, means for connectingsaid operators board with a calling line, and means controlled by theoperation of said mechanism to always disconnect said opera- ;ors boardbefore the call reaches the called 4. In a telephone system, a pluralityof telephone lines, an automatic switch mechanism common to said lines,responsive to any calling arty to extend connection from the callingline, a telephone common to all of said lines, means for connecting saidtelephone with a calling line, and means controlled by the operation ofsaid mechanism to always disconnect said telephone before the callreaches the called line.

5. In a telephone system, a plurality of telephone lines, an automaticswitch mechanism common to' said lines, responsive to any calling artyto extend connection from the calling ine, a signal common to all ofsaid lines, means for connecting said signal with a calling line, andmeans controlled b the operation of said mechanism to always disconnectsaid signal biefore the call reaches the called line.

6. In a telephone system, a plurality of telephone lines, an automaticswitch mechanism common to said lines, rwponsive to any calling party toextend connection from the calling l1ne,-an operators board common toall of said lines, means for connecting said operators board with acalling line, and means controlledby the operation of. said mechanism toalways disconnect said operators board before the call reaches thecalled line.

7. In a telephone system, a plurality of telephone lines, mechanismoperable under substation control to extend connection from calli linesto called lines, and disconnect there rom, a telephone for connectionwith every calling line, common to all of said lines, and meanscontrolled by the operation of said mechanism to always disconnect saidtelephone before the call reaches the called line, said mechanismcomprising a first selector in which said means are pro anism common tosaid lines,

every calling line, common to all of said lines, and means controlled bythe operation of said mechanism to always disconnect said signal beforethe-call reaches the called line, said mechanism comprlsing a, firstselector in whichsaid means are provided in the form of contacts whichcontrol the circuit of said signal.

9. In a-telephone system, a plurality of telephone lines, vmechanismoperable under substation control to extend connection fromcallinglinesto called'lines, and disconnecttherefrom, an operators boardfor connec tion with ever calling line, commonto all of said linesfandmeans controlled by the operation of said mechanism to alwaysdisconnect-said operators board before the call reachesthe calledline,said mechanism coinprising a tirstselecton-in 'which'said means areprovided in the form of contacts which control the circuit of saidoperators board.

10. In a telephone system, a plurality of telephone lines, an automaticswitch m'ecln anism eon'imon to said lines, "responsive to any callingparty to extend connection from the calling li n'e, 'ate'lephone for.connection with every calling line. ommoir to all of said lines, andmeans controlled by the'operation ofsaidmechanism to'alwa disconnectsaid telephone' before the cail reaches the called line, said mechanismcou'iprising a first selector in which meansare vided inthe form ofcontacts which "control the circuit of said telephone. I y

11. In atelephone system, a plurality of telephone lines, an automaticswitch 'meclr anism common to said lines, responsive to any callingparty to exte'nd coimeciiou from the calling line, a signal forconnection with every calling line, common to all of said lines, andmeans controlled by the operation of said mechanism to always disconnectsaid signal before the call reaches the. called line, said mechanismcomprising a first selectorin which said means are provided in the formofcontacts which control the circuit of said signal. 7 I

12. In a telephone systenna plurality of telephone-lines, an automatic.switch mechresponsive to any calling party to extend connection from thecalling line, an operators board for connection with every calling line,common to all of said lines, and means controlled by the i are providedin the form of contacts which control the circuit of said operatorsboard. 13. In a telephone system, a plurality of telephone lines, atelephone common to said lines, and means controllable from any callingsubstation to automatically connect the calling line with saidtelephone, and disconnect therefronaibet'ore the call reaches the calledline.

1-1, In a telephone system, a plurality of telephone lines, a telephonecommon to said lines, said telephone being connected with all calliiiglines over which the calls have notiprogressed beyond a certain point,and

disconnected from all calling lines over which the calls have progressedbeyond said point, said system being provided with means by which thesaid disconnection is controlled by the calling subscribers only.

15. In a telephone system, a plurality of telephone lines, a telephonecommon to said lines for the purpose of connection with all callinglines, means by which the removal. of the receiver at any callingsubstation connects the calling line with said telephone, a callingmechanism at the substation of each line, switches responsive to saidmechanism to extend the call from any calling line, and means controlledby the operation oi said switches to disconnect the said telephone fromthe calling line before the call reaches the calledline. i

16. In a telephone system, a plurality of telephone lines.'a telephonecoi'm'non to said lines, means whereby said telephone is operativelyconnected with all calling lines over which the calls have notprogressed beyond a. certain point, and means whereby the said telephoneis not in operative relation to any calling lines over which the callshave progressed beyond said point, said means beinguinder the control ofthe scribers only.

17. In a telephone system, a line. a telephone, a calling mechanism forsaid line. a hook switch for said line, means whereby the operation ofsaidhook switch connects calling subthe said line with said telephone,and means whereby the operation of said mechanism disconnects thetelephone from saidline.

18. In a telephone systcn'i, a plurality of first selectors, a telephonecommon to said selectors, connected therewith, and means on eachselector for opening the circuit of said telephone, said means beingoperated by the initial actuation of said selectors. 19. In a telephonesystem, a plurality of telephone lines, automatic switches controllableover said lines to extend calls there from, an operators telephonefor'listening in on all calling lines, and means controlled by saidselectorsfor preventing listening'in after the operation thereof.

20. In a telephone system, a' calling line, a calling mechanismtherefor, means respon-.

sive to said mechanism for extending the mon to a plurality of saidlines, a line relay for said switch, a second relay connected in serieswit-h said'line relay and adapted to be energized in series therewith,and an operators telephone set adapted to be con nceted throughsaidswitch to a subscriber's line upon the energization of said secondrelay.

22. Ina telephone system, a plurality of telephone lines, an automaticswitch common to a plurality of said lines, a line relay for saidswitch,'a second relay connected in series with said line relay andadapted to be energized in series therewith, an operators telephone setadapted to be connected through said switch to a subscribers line uponthe energization of said second relay, and normal contacts controlled bythe movement of said switch for again disconnecting said operatorstelephone set.

23. In a telephone system, a plurality of subscribers lines, anautomatic switch common to a. plurality of said lines having verticaland rotary motion, an operators set normally disconnected from saidswitch, a line relay for said switch, a" second relay adapted to beenergized in series with said line nelay for connecting said operatorsset with said switch, and ofi -normal contacts in the circuit of saidoperators set adapted to be opened by the first vertical movement ofsaid switch for again disconnecting said telephone set from the switch.

.24. In a telephone system, a plurality of subscribers lines, anautomatic switch common to a plurality of said lines, an operators setnormally disconnected fromsaid said switch, a douhle-u'mmd rela for saidswitch, a second double-wound re ay having one winding connected inseries with one of the windings of said line relay, the second windingof said second relay being'connected in series with said operatorstelephone, means for energizing said line relay and said second relaywhen saidswitch is seized to. connect said operators set with saidswitch, and contacts connected in series with said operators telephonecontrolled by the first movement of said switch to again disconnect saidtelephone from said switch.

In a telephone system, a-plurality of telephone lines, a telephonecommon to said lines, means controllable from any calling substation toauton'iatically connect .the call-- ing line with said telephone, anddisconnect therefrom, before the call reaches the called line, and meansfor preventing connection. of said telephone with called lines.

26. In a telephone system, a plurality of telephone lines, a tele honecommon to said lines, said telephone heing connected with all callinglines over which .the calls have not progressed beyond a certain oint,and disconnected from all callin v 'nes over which the calls haveprogresse' beyond said point, said system being rovided with means bywhich thesaid disconnection is controlled by the calling subscribersonly, and means for preventing connection of sand telephone with calledline's.

Signed byme at (Chicago, county, Illinois, this 15th day of'April, 1911.

ALEXANDER E. KEITHL 'Witnesses:

A rmen J. RAY, i E.'.D. Fangs.

